I was thinking it should be maybe two full pieces in the center, then two little more than half pieces on the ends. That would work right?

Two end pieces should orobably be same size (not full) -and I would guess the next piece to the right (on the angled wall) if possible should be the other half of the cut one, size wise, if that makes sense.

you'd have to see what the upper area needs. This low part at the bottom may have a smaller piece at the step, but the left hand side of the wall should not be slivers. The tile layout should be centered in the wall, as far as I'm aware. Where we are looking is not the center of the wall, somewhere above that is the center. Also the fact that there are not trimmed bottoms is something to be concerned about, because you may end up with slivers at the ceiling too. This person has not tiled before, or at least didn't learn to tile correctly. What is this you are tiling? If its a shower, is the blue a liquid water/vapor barrier? If it is, it should go up to include the top tile of you installation. And should be totally installed and dried the specified time, before tile installed.

After discussing options with my tiler I did choose to have some slightly larger slivers in every other row on one wall so that the wall's center lined up with the drain and so it looked like a full tile wrapped around wall corners so it looked a bit more uniformed tile size wise throughout the shower. I thought I made a mistake in my choice before the grout but after grout it is hardly noticeable to me now.

before grout

After

my tiler mapped out my tile lines for me to see before starting the tiles. You could ask him to do that.

On your picture the sliver bothers me less than how the floor grout lines intersect with the wall lines. To me they should be centered better.

That tile sliver is too small. They break easy when they are that small. @roarah's narrow tile isn't as narrow, and is an example of careful planning. The wall layout is centered. IMO if the cut piece would have been narrower, another layout option would need to be discussed. But I'm not a pro. There are options of 1/3 offset for staggered layouts that can influence the cut piece size.

Gorgeous shower @roarah!

Thanks enduring, your shower and tile were what I used as inspiration and showed my tiler and tile shop to find mine!

oh, and something else. I always figured out my top to bottom layout and placed a block of some sort on the wall where my first full height tile would start. Then the bottom cut tiles would be fitted in once the walls were installed and dried so I could take the ledger out from underneath.

This is my complete back wall before the top and bottom cuts were complete. I did that last. The green is the Hydroban moisture barrier. This is a staggered 1/3 layout. It is probably the same size area as @roarah, at 60" across (typical bathtub alcove). See how the tile is centered up and down and also across.

I had to plan for the drop in the floor from the tile pan, so I had to
be careful of that 3" difference as well when planning the layout:

Thanks everyone for the advice so far. After looking some more it looks like the center was started at the center of that shelf/step, and the tiles go outward from there and wrap around the walls. The sliver is pretty small, but hopefully it will be ok and I think it will be partially covered by the tile from the adjacent wall. I should have posted a zoomed out pic initially, but I think it may be OK like it is?

Great pictures by the way, I sure hope ours will turn out pretty like yours!

You'll need to click on my pics to understand visually what I was trying to state in the text. The images as presented in thread are not the full images.

I think the whole picture looks so much better than the one section you showed! It makes sense now. It is a pretty tub area!

Thank you!! I'm getting pretty excited :)